On 11/20/19 2:53 PM, Borislav Petkov wrote:
On Wed, Nov 20, 2019 at 02:23:49PM -0700, Dave Jiang wrote:
+/**
+ * iosubmit_cmds512 - copy data to single MMIO location, in 512-bit units
Where is the alignment check on that data before doing the copying?
I'll add the check on the destination address. The call is modeled after
__iowrite64_copy() / __iowrite32_copy() in lib/iomap_copy.c. Looks like
those functions do not check for the alignment requirements either.
+ * @dst: destination, in MMIO space (must be 512-bit aligned)
+ * @src: source
+ * @count: number of 512 bits quantities to submit
Where's that check on the data?
I don't follow?
+ *
+ * Submit data from kernel space to MMIO space, in units of 512 bits at a
+ * time. Order of access is not guaranteed, nor is a memory barrier
+ * performed afterwards.
+ */
+static inline void iosubmit_cmds512(void __iomem *dst, const void *src,
+ size_t count)
An iosubmit function which returns void and doesn't tell its callers
whether it succeeded or not? That looks non-optimal to say the least.
Why isn't there a fallback function which to call when the CPU doesn't
support movdir64b?
Because then you can use alternative_call() and have the thing work
regardless of hardware support for MOVDIR*.
Looks like Tony answered this part.
+{
+ const u8 *from = src;
+ const u8 *end = from + count * 64;
+
+ if (!cpu_has_write512())
If anything, that thing needs to go and you should use
static_cpu_has(X86_FEATURE_MOVDIR64B)
as it looks to me like you would care about speed on this fast path?
Yes, no?
Yes thank you!
